Standards for serially transmitting AV data between devices connected together via a cable include DVI (Digital Visual Interface) and HDMI (High Definition Multimedia Interface). DVI is a standard for serially transmitting video data. HDMI is backward compatible with DVI, and allows for serial transmission of audio data in addition to video data. With a transmission system in conformity with these standards, a parallel data signal representing video and audio is converted in the transmitter apparatus to a serial data signal in synchronism with a clock signal inside the transmitter apparatus, and the serial data signal and the clock signal are transmitted to the receiver apparatus. The data signal is transmitted at a relatively high frequency since it is parallel/serial-converted, whereas the clock signal is transmitted at a relatively low frequency, i.e., the same frequency as the parallel data signal. Then, in the receiver apparatus, a data recovery clock signal is produced from the received clock signal, and the received serial data signal is converted to a parallel data signal in synchronism with the produced clock signal. Thus, AV data being parallel data is serially transmitted from the transmitter apparatus to the receiver apparatus (see, for example, Patent Document 1).
The clock transmission schemes for the above transmission system include the coherent clocking scheme and the non-coherent clocking scheme. In the coherent clocking scheme, a clock signal obtained by dividing the frequency of a clock signal produced for parallel/serial conversion is transmitted. For example, with 10-bit parallel/serial conversion, the transmitter apparatus produces a 10-times clock signal by multiplying the frequency of the reference clock signal being in synchronism with the parallel data signal by 10, and a clock signal obtained by dividing the frequency of the 10-times clock signal by 10 is transmitted to the receiver apparatus. In the non-coherent clocking scheme, a clock signal in synchronism with the parallel data signal is transmitted as it is. For example, with 10-bit parallel/serial conversion, while the transmitter apparatus produces a 10-times clock signal by multiplying the frequency of the reference clock signal being in synchronism with the parallel data signal by 10, the reference clock signal is transmitted to the receiver apparatus.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-314970